Hybrid beamforming systems include elements of in both the analog and digital domains. Antenna ports with radio frequency (RF) chains provide the full capability of digital beamforming while arrays of antenna elements with phase shifters provide the capability of analog beamforming. Hybrid beamforming is expected to achieve the high performance of full digital massive multiple input multiple output (MIMO) while minimizing the high costs associated with the RF chains in digital beamforming.
Current solutions to hybrid precoding design for a hybrid beamforming system include a fixed analog beamforming that is set according to the down tilt of the antenna array or generating analog and digital beamforming by nonlinear iteration optimizations/exhaustive search. The former has the benefit of a low precoding complexity, but it cannot achieve high system performance. The latter can achieve high system performance, but it has an extremely high precoding complexity, especially for an orthogonal frequency-division multiple access (OFDMA) multi-user MIMO system. Due to multiple users and multiple subcarriers which need to be considered, these iteration optimization-based hybrid precoding techniques experience unacceptably high computational complexity. Moreover, convergence of the iterations cannot be guaranteed.
The subject matter disclosed herein provides a device and a method for hybrid beamforming precoding with high system performance while minimizing precoding complexity.